Design of the circularly polarized ceramic antenna, suitable for GPS system, on an asymmetric ground plane is presented in this thesis. Firstly, to obtain two isolated ground planes, we insert an L slit on an asymmetric ground plane, making the antenna with a symmetric ground plane. Then, we isolate the excited surface current between the two ground planes by using a quarter-wavelength mini-coaxial cable. The surface current can distribute uniformly on the ground plane when the proposed antenna is in operation, which makes possible a good circularly polarized radiation pattern in the operation band.

For laptop computers, the conventional internal antennas are usually used to operate in the WLAN system only, which can not provide sufficient and seamless services for wireless users. In order to overcome this problem, we propose some internal antennas having dual-/multi-network operation capability in this dissertation. Firstly, we present a combo antenna, which combines two shorted monopole antennas for operating in the WWAN/WLAN dual-network system. Secondly, we introduce a shorted monopole antenna through adding a parasitic element to enhance the impedance bandwidth for operating in the WLAN/WiMAX dual-network system. Thirdly, for achieving the compact-size antenna, we present a composite antenna which is composed of a ceramic chip and a printed radiating portion. Fourthly, we introduce a wideband shorted monopole antenna which can provide a wide bandwidth to cover the WPAN, WLAN, and WiMAX operations, and apply it to the MIMO system. Finally, we propose a coupling-type monopole antenna having multi-network operation capability and a compact size, which is about the smallest antenna for wideband operation in the laptop computer so far.